Noise and Environment
When such glass breaks, small granular fragments are formed which remain glued to the interlayer.
Transparent panels are ideal for reducing or completely eliminating the visual impact of a noise barrier; however, their costs can be 20 times higher than those made of concrete or steel. The justification for their high cost can be found in improving safety in places where opaque noise barriers can have a negative effect on visibility. These types of panels are more sensitive to damage from flying debris and abrasive action as a consequence of the sandblasting effect that is inevitably due to the swirling dust that is always present on the pavement layer.
2.3.5 Plastic
There are several types of plastic materials available and often used in the construction of noise barriers: polyethylene, PVC (polyvinyl chloride) and fibre- glass. Plastic panels can be installed in almost any situation due to their extremely low mass, easiness to mould and weatherproof features. Bearing in mind all of the aforementioned, they are increasingly used for the construction of noise barriers, especially those of a more complex shape. The problem with plastic materials is a slightly lower structural strength and flammability, i.e. the smoke and gases pro- duced by the combustion of plastics are very toxic.
2.3.6 Composite materials
Composite materials for noise barriers can be defined as any product composed of two or more “basic” materials, for example, wood mixed with concrete and then placed on a concrete foundation. By combining basic materials, the characteristics of the final product (noise barriers) and its durability, and even in some cases safety, are altered.
Material Thickness
(mm) Weight
(kg/m2) Transmission loss (dBA)
Concrete Block, 200 mm × 200 mm × 405 mm 200 151 34
Dense Concrete 100 244 40
Steel 1,27 10 25
Steel 0,95 7,3 22
Steel 0,79 6,1 20
Iron 0,64 4,9 18
Aluminium 1,59 4,4 23
Aluminium 3,18 8,8 25
Aluminium 6,35 17,1 27
Wood (Fir) 12 8,3 18
Wood (Fir) 25 16,1 21
Wood (Fir) 50 32,7 24
Plywood 12 8,3 20
Plywood 25 16,1 23
Glass 3,18 7,8 22
Plexiglas 6 7,3 22
Table 1.
Approximate values of transmission loss parameter for different types of materials.
Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056 2.4 Noise barriers transmission loss (TL)
Typical values of the noise barriers transmission loss (TL) parameter when looking at the A-weighted characteristic are from 10 dBA to 15 dBA. Noise bar- riers should be constructed of materials with a minimum density of 20 kg m2. A density of 20 kg/m2 can be achieved by lighter and thicker or heavier and thinner materials (i.e. higher material density enables a thinner material). Table 1 gives the approximate TL values for some common materials, tested for a typical A-weighted highway traffic frequency spectrum [16]. These values can be used as a rough guideline in designing noise barriers. For more accurate values, one would need to find material testing reports from authorised laboratories.
Noise and Environment
When such glass breaks, small granular fragments are formed which remain glued to the interlayer.
Transparent panels are ideal for reducing or completely eliminating the visual impact of a noise barrier; however, their costs can be 20 times higher than those made of concrete or steel. The justification for their high cost can be found in improving safety in places where opaque noise barriers can have a negative effect on visibility. These types of panels are more sensitive to damage from flying debris and abrasive action as a consequence of the sandblasting effect that is inevitably due to the swirling dust that is always present on the pavement layer.
2.3.5 Plastic
There are several types of plastic materials available and often used in the construction of noise barriers: polyethylene, PVC (polyvinyl chloride) and fibre- glass. Plastic panels can be installed in almost any situation due to their extremely low mass, easiness to mould and weatherproof features. Bearing in mind all of the aforementioned, they are increasingly used for the construction of noise barriers, especially those of a more complex shape. The problem with plastic materials is a slightly lower structural strength and flammability, i.e. the smoke and gases pro- duced by the combustion of plastics are very toxic.
2.3.6 Composite materials
Composite materials for noise barriers can be defined as any product composed of two or more “basic” materials, for example, wood mixed with concrete and then placed on a concrete foundation. By combining basic materials, the characteristics of the final product (noise barriers) and its durability, and even in some cases safety, are altered.
Material Thickness
(mm) Weight
(kg/m2) Transmission loss (dBA)
Concrete Block, 200 mm × 200 mm × 405 mm 200 151 34
Dense Concrete 100 244 40
Steel 1,27 10 25
Steel 0,95 7,3 22
Steel 0,79 6,1 20
Iron 0,64 4,9 18
Aluminium 1,59 4,4 23
Aluminium 3,18 8,8 25
Aluminium 6,35 17,1 27
Wood (Fir) 12 8,3 18
Wood (Fir) 25 16,1 21
Wood (Fir) 50 32,7 24
Plywood 12 8,3 20
Plywood 25 16,1 23
Glass 3,18 7,8 22
Plexiglas 6 7,3 22
Table 1.
Approximate values of transmission loss parameter for different types of materials.
Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056 2.4 Noise barriers transmission loss (TL)
Typical values of the noise barriers transmission loss (TL) parameter when looking at the A-weighted characteristic are from 10 dBA to 15 dBA. Noise bar- riers should be constructed of materials with a minimum density of 20 kg m2. A density of 20 kg/m2 can be achieved by lighter and thicker or heavier and thinner materials (i.e. higher material density enables a thinner material). Table 1 gives the approximate TL values for some common materials, tested for a typical A-weighted highway traffic frequency spectrum [16]. These values can be used as a rough guideline in designing noise barriers. For more accurate values, one would need to find material testing reports from authorised laboratories.
3. A contemporary approach: soundscape
The soundscape concept has been introduced to modify and complement the assessment of noise and its effects on humans. From the beginning, soundscape research has questioned the limits of existing acoustic measurements and the cultural dimension which Schafer included in his research for the first time in the 1960s [17].
3.1 Soundscape definition
A particular soundscape includes all the sounds from a certain acoustic environ- ment received by the human ear. The first idea of soundscape was introduced by Schafer, in his book The New Soundscape [17]. His primary idea was to record a soundscape of the world in a form of a map similar to geographical maps. However, extremely rapid changes in the soundscapes have made this idea impossible to implement. Soundscapes, among other things, change rapidly due to the growth of the human population, people’s migration and traffic increase. On the other hand, it is possible and of great interest to record current soundscapes.
The soundscape of a certain environment consists of various sound groups and sound sources. They can be divided into three major groups, biophony, geophony and anthrophony [17], which is shown in Figure 8.
Biophony are all the sounds produced by living organisms in their natural habitat (Table 2). It is by far the most complex feature of soundscape because it combines all biological sound sources, from microscopic to large fauna that live in a given environment for a certain period of time. In environments that are rich with different voices of living beings, organisms produce acoustic signals in different spatial relationships which can sound as one or more sound signals. Geophony are all-natural sounds coming from non-biological sources in a certain environment (Table 2). Generally, they can be divided into four types: the sound effects of wind, water, climate and geophysical forces. Anthrophony are all sounds generated by humans in any natural environment. This group includes sounds coming from people, music and traffic noise.
Bearing in mind all of the aforementioned, it can be concluded that the concept of soundscape as a field of research is extremely broad and requires a multidisciplinary approach. In studies and researches, apart from acoustic engineers, psychologists, physicians, builders, architects and sociologists should be involved.
Table 2 shows sound sources or acoustic components and direct acoustic effects of non-anthropogenic sound elements (biophony and geophony).
Noise and Environment
3.2 Soundscape classification
The most common soundscape classification is the one with respect to the related environment, and therefore we can distinguish them as follows (Figures 9 and 10):
a. Natural soundscapes (e.g. marine, forest soundscape, etc.) b. Rural soundscapes.
c. Urban soundscapes.
Weather
RS: wind, rain, thunder, earthquake, clouds
D: sound propagation, absorption, reflection, refraction, diffusion, diffraction, masking Animals
S: sound of animals: birds, mammals, insects, reptiles, amphibians; moving of animals: running, flying, jumping, landing; non-voice expressions: moving of insects’ wings
D: sound propagation, masking Nature
S: rivers and streams, waves, flux and reflux, vegetation excitation e.g. leaf rustle, falling of trees D: propagation of sound, masking, absorption, reflection, refraction, diffusion, diffraction Terrain
S: barriers, dams
D: propagation of sound, absorption, reflection, refraction, diffusion, diffraction S—Sound sources or acoustic components and D—direct acoustic effects.
Table 2.
Characteristics of non-anthropogenic sound elements (based on [17]) Figure 8.
Soundscape composition.
Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056
Considering the way and style of today’s life, it can be concluded that the urban soundscape is most explored and is changing in a fast pace. A city’s soundscape encompasses all three active components which describe a certain soundscape;
however, the largest impact is anthropogenic, i.e. sounds generated by various human activities. Looking through history, after the industrial and electrical revolution, the look and sound of the city have changed remarkably. Today a similar thing is happening, however as a result of the accelerated construction work and overcrowding of cities. One of the biggest problems in the city has become noise, and the biggest source of this noise is traffic [19].
3.3 How to record a soundscape?
One of the possible ways to record a soundscape is the soundwalk method.
Soundwalk method, as a concept, was first introduced by an urban planner Kevin
Figure 9.
Soundscape classification.
Figure 10.
Description of soundwalking (based on [18]).
Noise and Environment
3.2 Soundscape classification
The most common soundscape classification is the one with respect to the related environment, and therefore we can distinguish them as follows (Figures 9 and 10):
a. Natural soundscapes (e.g. marine, forest soundscape, etc.) b. Rural soundscapes.
c. Urban soundscapes.
Weather
RS: wind, rain, thunder, earthquake, clouds
D: sound propagation, absorption, reflection, refraction, diffusion, diffraction, masking Animals
S: sound of animals: birds, mammals, insects, reptiles, amphibians; moving of animals: running, flying, jumping, landing; non-voice expressions: moving of insects’ wings
D: sound propagation, masking Nature
S: rivers and streams, waves, flux and reflux, vegetation excitation e.g. leaf rustle, falling of trees D: propagation of sound, masking, absorption, reflection, refraction, diffusion, diffraction Terrain
S: barriers, dams
D: propagation of sound, absorption, reflection, refraction, diffusion, diffraction S—Sound sources or acoustic components and D—direct acoustic effects.
Table 2.
Characteristics of non-anthropogenic sound elements (based on [17]) Figure 8.
Soundscape composition.
Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056
Considering the way and style of today’s life, it can be concluded that the urban soundscape is most explored and is changing in a fast pace. A city’s soundscape encompasses all three active components which describe a certain soundscape;
however, the largest impact is anthropogenic, i.e. sounds generated by various human activities. Looking through history, after the industrial and electrical revolution, the look and sound of the city have changed remarkably. Today a similar thing is happening, however as a result of the accelerated construction work and overcrowding of cities. One of the biggest problems in the city has become noise, and the biggest source of this noise is traffic [19].
3.3 How to record a soundscape?
One of the possible ways to record a soundscape is the soundwalk method.
Soundwalk method, as a concept, was first introduced by an urban planner Kevin
Figure 9.
Soundscape classification.
Figure 10.
Description of soundwalking (based on [18]).
Noise and Environment
Lynch [20, 21]. His idea was to follow the usual routes which people use on their commute and which are specific to places of interest with the goal of “capturing”
their soundscape. The usual recording of a soundscape has the duration of 30 min- utes. The 30-minute choice corresponds to the distance a man would walk across in an average European city and, on the other hand, keeps a certain homogeneity as far as activities in that particular soundscape are concerned. Recording takes place several times a day, for several days, however always at a nice and dry weather.
Depending on the research premises, the question how to exactly and accurately process the data obtained from the recordings remains. Although most scientists in their studies claim that the soundwalk “walks” lasted for an average of 15 minutes, it is possible to record soundscapes for a longer period depending on the focus and goal of the research. It is also possible to “cut” or shorten the longer soundscape record- ings and apply other acoustic “tools” to the soundscape recordings.
The soundwalk method uses a recorder and a pair of binaural microphones places in the ears of the person who is performing the soundwalks, i.e. soundwalker. The soundwalker, as the name suggests, performs “walks” through a certain environ- ment. The soundwalker needs to carefully breath while walking, and this kind of recording is performed normally in dry and sunny weather, unless we want to record a certain natural manifestation, such as rain. Recording is performed at the height of the walker (the binaural microphones are placed in the ears of the walker) and therefore the recorded signals are similar (at the highest possible level) to the signals heard by the pedestrians in that environment (Figure 11).
There is still no consensus among scientists regarding the recording length of the soundscape. Namely, there is no clearly defined time limit that would determine the difference between authentically play backed soundscapes while simultaneously avoiding the listener’s fatigue. Reproduction of soundscapes in terms of its length depends on the researcher and the purpose of his research from a few minutes to several hours.
3.4 Soundscape analysis
Alongside the soundwalk method, the researchers usually perform the analysis of the recorded soundscape with the “help” of the questionnaire which is again not defined by any standard or norm. The concept of the questionnaire, whose purpose is a detailed analysis provided by the listener, is not clearly defined, and moreover it depends again on research premises and focus [22–24]. Questionnaires vary from direct questions to listeners about the soundscape, requirements for a more detailed descriptions of the soundscape in terms of defining them as pleasant or unpleasant, attributes that may or may not be related to mathematical scales and adjective pairs that are not standardised so each researcher can use “their own” adjective pairs which they consider to best describe the soundscape and fit their research. An example of questionnaire [25] which uses bipolar adjective pairs is shown in Table 3.
Figure 12 shows an example of performed soundscape analysis, in particu- lar an expressway which stretches from the east to the west exit of the Zagreb, capital of Croatia [26]. To be more precise, Figure 12 shows a photograph of the recorded location using the soundwalking method, the route of the soundwalker, the spectrogram of the recording and the sound sources which were characterised as distracting obtained through a specially designed questionnaire for that particular research [26].
To sum it up, the questionnaires are not an objective acoustic parameter; how- ever, they present a good measure of the listener’s perception of the soundscape. A major problem is how to correlate such a subjective parameter with objective acous- tic parameters, i.e. loudness, sharpness, roughness and fluctuation strength [27].
Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056
3.5 Using the soundscape as a noise reduction instrument
The ISO 12913-1 standard defines soundscapes as acoustic environments “as perceived by people, in context”. Thus, nowadays more and more soundscape studies are oriented towards human health, well-being and overall quality of life [28–31]. In addition, the WHO Environmental Noise Guidelines for the European Region provide certain guidance on protecting human health from harmful exposure to environmental noise. The guidelines strongly recommend reducing the noise levels (Lden and Lnight) for the cases of environmental noise sources such as road traffic noise, railway noise, aircraft noise, wind turbine noise and leisure noise [32]. In the past the only possible approach to resolve this issue and reduce noise levels in an efficient way has been noise barriers which have been described thoroughly in previous sections. However, in order to construct and position an effective noise barrier, first one needs to have enough space for it, i.e. noise bar- riers can serve as a solutions only if they are planned before the actual building which is today a quite rare case scenario. In addition, if there is an opportunity to incorporate a noise barrier into an existing urban environment, researchers should take into account the “visual pleasantness” as well as the economic feasibility of the noise barrier.
Figure 11.
An example of the soundwalker’s route.
Pair no. Assigned bipolar adjective pair Type of pair
1 quiet – loud Auditory
2 deep - high-pitched
3 diverse - monotonous
4 pleasant - unpleasant Emotional
5 dynamic – calm
6 natural - artificial
7 harmonious - chaotic
8 appealing - repulsive
9 soothing - stressful
10 conspicuous – inconspicuous
11 gentle – rough
Table 3.
The adjective pairs used in questionnaire [25].
Noise and Environment
Lynch [20, 21]. His idea was to follow the usual routes which people use on their commute and which are specific to places of interest with the goal of “capturing”
their soundscape. The usual recording of a soundscape has the duration of 30 min- utes. The 30-minute choice corresponds to the distance a man would walk across in an average European city and, on the other hand, keeps a certain homogeneity as far as activities in that particular soundscape are concerned. Recording takes place several times a day, for several days, however always at a nice and dry weather.
Depending on the research premises, the question how to exactly and accurately process the data obtained from the recordings remains. Although most scientists in their studies claim that the soundwalk “walks” lasted for an average of 15 minutes, it is possible to record soundscapes for a longer period depending on the focus and goal of the research. It is also possible to “cut” or shorten the longer soundscape record- ings and apply other acoustic “tools” to the soundscape recordings.
The soundwalk method uses a recorder and a pair of binaural microphones places in the ears of the person who is performing the soundwalks, i.e. soundwalker. The soundwalker, as the name suggests, performs “walks” through a certain environ- ment. The soundwalker needs to carefully breath while walking, and this kind of recording is performed normally in dry and sunny weather, unless we want to record a certain natural manifestation, such as rain. Recording is performed at the height of the walker (the binaural microphones are placed in the ears of the walker) and therefore the recorded signals are similar (at the highest possible level) to the signals heard by the pedestrians in that environment (Figure 11).
There is still no consensus among scientists regarding the recording length of the soundscape. Namely, there is no clearly defined time limit that would determine the difference between authentically play backed soundscapes while simultaneously avoiding the listener’s fatigue. Reproduction of soundscapes in terms of its length depends on the researcher and the purpose of his research from a few minutes to several hours.
3.4 Soundscape analysis
Alongside the soundwalk method, the researchers usually perform the analysis of the recorded soundscape with the “help” of the questionnaire which is again not defined by any standard or norm. The concept of the questionnaire, whose purpose is a detailed analysis provided by the listener, is not clearly defined, and moreover it depends again on research premises and focus [22–24]. Questionnaires vary from direct questions to listeners about the soundscape, requirements for a more detailed descriptions of the soundscape in terms of defining them as pleasant or unpleasant, attributes that may or may not be related to mathematical scales and adjective pairs that are not standardised so each researcher can use “their own” adjective pairs which they consider to best describe the soundscape and fit their research. An example of questionnaire [25] which uses bipolar adjective pairs is shown in Table 3.
Figure 12 shows an example of performed soundscape analysis, in particu- lar an expressway which stretches from the east to the west exit of the Zagreb, capital of Croatia [26]. To be more precise, Figure 12 shows a photograph of the recorded location using the soundwalking method, the route of the soundwalker, the spectrogram of the recording and the sound sources which were characterised as distracting obtained through a specially designed questionnaire for that particular research [26].
To sum it up, the questionnaires are not an objective acoustic parameter; how- ever, they present a good measure of the listener’s perception of the soundscape. A major problem is how to correlate such a subjective parameter with objective acous- tic parameters, i.e. loudness, sharpness, roughness and fluctuation strength [27].
Innovative Approaches to Noise Reduction DOI: http://dx.doi.org/10.5772/intechopen.93056
3.5 Using the soundscape as a noise reduction instrument
The ISO 12913-1 standard defines soundscapes as acoustic environments “as perceived by people, in context”. Thus, nowadays more and more soundscape studies are oriented towards human health, well-being and overall quality of life [28–31]. In addition, the WHO Environmental Noise Guidelines for the European Region provide certain guidance on protecting human health from harmful exposure to environmental noise. The guidelines strongly recommend reducing the noise levels (Lden and Lnight) for the cases of environmental noise sources such as road traffic noise, railway noise, aircraft noise, wind turbine noise and leisure noise [32]. In the past the only possible approach to resolve this issue and reduce noise levels in an efficient way has been noise barriers which have been described thoroughly in previous sections. However, in order to construct and position an effective noise barrier, first one needs to have enough space for it, i.e. noise bar- riers can serve as a solutions only if they are planned before the actual building which is today a quite rare case scenario. In addition, if there is an opportunity to incorporate a noise barrier into an existing urban environment, researchers should take into account the “visual pleasantness” as well as the economic feasibility of the noise barrier.
Figure 11.
An example of the soundwalker’s route.
Pair no. Assigned bipolar adjective pair Type of pair
1 quiet – loud Auditory
2 deep - high-pitched
3 diverse - monotonous
4 pleasant - unpleasant Emotional
5 dynamic – calm
6 natural - artificial
7 harmonious - chaotic
8 appealing - repulsive
9 soothing - stressful
10 conspicuous – inconspicuous
11 gentle – rough
Table 3.
The adjective pairs used in questionnaire [25].